This invention relates to a disc brake and, particularly to a pad spring in a disc brake.
One typical prior art disc brake comprises a carrier or a stationary member adapted to be secured to a non-rotatable part of a vehicle at one side of a rotatable disc, a pair of friction pads disposed on opposite sides of the disc and slidably supported on the carrier for movement in the direction parallel to the axis of the disc, and a caliper supported on the carrier to slide in the direction parallel to the axis of the disc. The caliper has a generally inverted U-shaped configuration with one limb portion incorporating therein a hydraulic piston and cylinder mechanism for pressing one friction pad against one side surface of the disc, another limb portion being located contiguous to the rear surface of the other friction pad for pressing it against the other side surface of the disc and a bridge portion straddling the outer circumference of the disc and connecting integrally the two limb portions. Further, the carrier comprises two circumferentially spaced leg portions for supporting thereon the friction pads. The leg portions also straddle the outer circumference of the disc at locations on the opposite sides of the bridge portion of the caliper.
There is provided a pad spring in such disc brake for preventing the vibrations of the friction pad and assuring smooth sliding movement thereof relative to the carrier. It has been proposed to form the pad spring of a sheet metal with a base portion contacting and extending along a side surface of the leg portion, a retaining portion extending from the base portion and engaging with the leg portion and a pressing portion extending from the base portion and resiliently engaging with the radially outward surfaces of the friction pad. The friction pad is biased against the leg portion of the carrier by the spring force of the pressing portion, whereby the relative sliding movement of the friction pad is smooth and vibrations can reliably be prevented. However, there are shortcomings in that when the pressing portion is excessively deformed due to excessive vibrations or errors in the assembling or deassembling operation, the spring force of the pressing portion is decreased. Such shortcomings can be prevented by increasing the strength of the pressing portion, but this excessively increases the spring force and, accordingly the sliding resistance between the friction pad and the carrier increases and, further, since the spring constant increases also, the deviation in the dimension of the pad spring may sometimes have excessive effects on the spring force and it is difficult to control the spring force so that it is in a desired range.